We will continue to study the inheritance and expression of mouse immunoglobulin structural genes in clones of normal and neoplastic (plasmacytomas) antibody cells, and in congenic strains of mice that have different immunoglobulin structural genes. For this purpose, we have adapted a solid-phase radioimmune assay which will enable us to quantitate the weights of specific IgG allotypes and idiotypes relative to the total weight of IgG class present.